Use of a composition containing at least one oxidation-sensitive hydrophilic active principle and at least one N-vinylmidazole polymer or copolymer

ABSTRACT

The invention relates to the use of a composition containing, in a physiologically acceptable medium having an aqueous phase, at least one oxidation-sensitive hydrophilic active principle selected from the group consisting of ascorbic acid and its derivatives and at least one non-crosslinked N-vinylimidazole polymer or copolymer, the active principle and the polymer or copolymer both being in the aqueous phase, for preventing or combatting the harmful effects of UV radiation and/or of pollution on the skin, in particular loss of firmness and/or of elasticity of the skin.

FIELD OF THE INVENTION

[0001] The present invention relates to the use of a compositioncomprising at least one oxidation-sensitive hydrophilic active principleand at least one N-vinylimidazole polymer or copolymer in aphysiologically acceptable medium comprising an aqueous phase.Preferably the use is cosmetic or dermatological, and preferably relatesto treating the skin and/or mucous membranes against UV, pollution, freeradicals, and sunburn.

BACKGROUND OF THE INVENTION

[0002] It is known to introduce, into cosmetic compositions, variousactive principles intended to contribute specific treatments to the skinand/or hair. However, some of these active principles exhibit thedisadvantage of being unstable in an aqueous medium and of easilydecomposing on contact with water, in particular because of oxidationphenomena. They thus rapidly lose their activity over time and thisinstability conflicts with the desired effectiveness.

[0003] Attempts have thus been made for a long time to formulateascorbic acid or vitamin C because of its numerous beneficialproperties. In particular, ascorbic acid stimulates the synthesis of theconnective tissue and in particular of collagen, strengthens thedefences of the cutaneous tissue against external attacks, such asultraviolet radiation and pollution, compensates for vitamin Edeficiency of the skin, depigments the skin and has a role in combattingfree radicals. These last two properties make it an excellent candidateas cosmetic or dermatological active principle for combatting ageing ofthe skin or for preventing ageing of the skin. Unfortunately, because ofits chemical structure (of α-ketolactone), ascorbic acid is highlysensitive to certain environmental parameters and in particular tooxidation phenomena. There thus ensues rapid decomposition of formulatedascorbic acid in the presence of these parameters and in particular inthe presence of oxygen, light or metal ions, as a function of thetemperature or under certain pH conditions (Pharm. Acta. Helv., 1969,44, 611-667; STP Pharma, 1985, 4, 281-286).

[0004] Several solutions have thus been envisaged in the prior art forreducing and/or slowing down the decomposition of ascorbic acid.

[0005] Provision has thus been made to use ascorbic acid in the form ofa chemical derivative (magnesium ascorbyl phosphate or esters of fattyacids and ascorbic acid), but the bioavailability of these derivativesis very low (J. Am. Acad. Dermatol., 1996, 34, 29-33).

[0006] The instability of ascorbic acid with respect to oxygen can beimproved by using specific packagings, such as twin compartments underan inert atmosphere, as disclosed in U.S. Pat. No. 5,935,584, oralternatively by the use of two-phase emulsions, one phase of which iscomposed of a dry powder comprising ascorbic acid and the second phaseof which is a liquid phase. The mixing of the two phases has to becarried out at the time of use (WO 98/43598). These solutions havedisadvantages with regard to the cost and the complexity of themanufacturing operations and significant restrictions with regard touse.

[0007] Another solution provided in the prior art consists in using ahigh concentration of glycols or polyols in order to reduce thesolubility of oxygen in the formulation, thus protecting the ascorbicacid (WO 96/24325, EP 0 755 674, U.S. Pat. No. 5,981,578). The polyolscan optionally be incorporated in liposomes, as disclosed in U.S. Pat.No. 6,020,367. However, these solutions exhibit the disadvantage ofresulting in sticky formulations, the cosmetic quality of which isdifficult to improve. Furthermore, the presence of a high concentrationof these compounds can lead to phenomena of irritation.

[0008] Ascorbic acid can also be formulated in anhydrous media, such assilicones (U.S. Pat. No. 6,194,452), which are capable of creating ananhydrous barrier around ascorbic acid. A major disadvantage of suchsolutions results from the lack of freshness on application.

[0009] The need thus remains for a composition employable in particularin the cosmetics field, in which a hydrophilic active principle which isunstable in an oxidizing medium is stabilized, which is comfortable onapplication, which does not lead to any skin irritation afterapplication and which is compatible with the constraints of anindustrial implementation of its manufacturing process.

[0010] Cutaneous ageing of physiological nature can be accelerated byenvironmental factors, such as repeated exposure of the skin tosunlight, in particular to ultraviolet A radiation, or to pollution, inparticular to diesel particles or to cigarette smoke. The action of theenvironment on the constituents of the skin (fibres, cells, enzymes) andon the sebum secreted by the skin results in particular in the formationof oxygen free radicals. In point of fact, these radicals result insignificant oxidative damage, in particular in cell membranes(permeability of the membranes), cell nuclei (destruction of DNA), andtissues, in particular connective tissue (decomposition of elastin andcollagen fibres). This damage results in particular in the loss offirmness and elasticity of the skin.

[0011] Ascorbic acid, by trapping free radicals, protects biologicalmolecules. Thus, applied topically, it can accumulate in the skin andcan restore the disrupted concentration of ascorbic acid, for example inthe case of exposure to UV radiation. It can, moreover, protect the skinfrom damage induced by UV radiation (British Journal of Dermatology,127, 1992, p. 247-253) or by environmental stress.

[0012] In parallel with this activity, ascorbic acid has an inhibitoryeffect on the secretion of the pro-inflammatory cytokines IL1 and IL6induced by UV radiation (Journal of Investigative Dermatology, 108(3),1997, p. 302-308). It is therefore of particular advantage as soothingagent for sunburn.

OBJECTS OF THE INVENTION

[0013] One object of the present invention is to provide a compositioncomprising an oxidation-sensitive active principle selected from thegroup consisting of ascorbic acid and its derivatives, which exhibitsgood cosmetic properties, both with regard to touch and with regard totolerance, the preservation of which over time does not require specificprecautions, and which retains the activity in combatting free radicalsof the said active principle, for preventing or combatting the harmfuleffects of UV radiation and/or of pollution on the skin, in particularthe loss of firmness and/or of elasticity of the skin.

DETAILED DESCRIPTION OF THE INVENTION

[0014] The inventors have discovered that the use of non-crosslinkedN-vinylimidazole polymers or copolymers in compositions in which theaqueous phase includes an oxidation-sensitive active principle, such asascorbic acid or one of its derivatives, makes it possible to achievethe abovementioned object.

[0015] In the prior art, some compounds having an imidazole structurehave been disclosed for their stabilizing properties. Thus, in PatentApplication EP 0 586 106, several imidazole-based molecules are used tostabilize certain retinoids against chemical decomposition. Furthermore,polymeric emulsifiers composed of N-vinylimidazole, of alkyl acrylatesand of vinyl acetates are disclosed in U.S. Pat. No. 4,057,622. They areused for the purpose of replacing known emulsifiers in order to overcometheir disadvantages, in particular with regard to smell, and tostabilize water-in-oil emulsions. Finally,N-vinylimidazole/N-vinylcaprolactam/N-vinylpyrrolidone copolymers aredisclosed in U.S. Pat. No. 6,191,188. They are used in the manufactureof hair-strengthening compositions.

[0016] To the knowledge of the inventors, polymers or copolymerscomprising N-vinylimidazole units have never been used in combinationwith hydrophilic active principles sensitive to decomposition byoxidation for the purpose of improving their stability in an aqueousmedium. This is true in particular in the case of ascorbic acid.

[0017] One embodiment of the present invention is therefore the cosmeticand/or dermatological use, for preventing or combatting the harmfuleffects of UV radiation and/or of pollution on the skin, of acomposition comprising, in a physiologically acceptable mediumcomprising an aqueous phase, at least one oxidation-sensitivehydrophilic active principle selected from the group consisting ofascorbic acid and its derivatives and at least one non-crosslinkedN-vinylimidazole polymer or copolymer, the said active principle and thesaid polymer or copolymer both being in the aqueous phase. The copolymeris present in an amount sufficient to stabilize the saidoxidation-sensitive hydrophilic active principle.

[0018] Another embodiment of matter of the present invention is thepreferably cosmetic and/or dermatological use, for preventing orcombatting loss of firmness and/or of elasticity of the skin, of acomposition comprising, in a physiologically acceptable mediumcomprising an aqueous phase, at least one oxidation-sensitivehydrophilic active principle selected from the group consisting ofascorbic acid and its derivatives and at least one non-crosslinkedN-vinylimidazole polymer or copolymer, the active principle and thepolymer or copolymer both being in the aqueous phase.

[0019] Another embodiment of the present invention is the use of acombination composed of at least one oxidation-sensitive hydrophilicactive principle selected from the group consisting of ascorbic acid andits derivatives and of at least one non-crosslinked N-vinylimidazolepolymer or copolymer in the aqueous phase of a composition as agent forcombatting free radicals.

[0020] Another embodiment of the present invention is the use of acombination composed of at least one oxidation-sensitive hydrophilicactive principle selected from the group consisting of ascorbic acid andits derivatives and of at least one non-crosslinked N-vinylimidazolepolymer or copolymer in the aqueous phase of a composition as soothingagent for sunburn.

[0021] The term “pollution” as used herein is understood to mean both“external” pollution, for example due to diesel particles, to ozone orto heavy metals, an “internal” pollution, which can in particular be dueto emissions of solvents from paints, from fitted carpet adhesives, frominsulation or from wallpaper (such as toluene, styrene, xylene orbenzaldehyde), or to cigarette smoke. This is because all thesepollutants are capable, directly or indirectly, of generating freeradicals.

[0022] According to the invention, the term “hydrophilic activeprinciple” is understood to mean a compound having a solubility in waterof at least 0.25% at ambient temperature (25° C.).

[0023] According to the invention, the term “oxidation-sensitivehydrophilic active principle” is understood to mean any active principleof natural or synthetic origin capable of undergoing decomposition by anoxidation mechanism. This oxidation phenomenon can have several causes,in particular the presence of oxygen, of light or of metal ions, a hightemperature or certain pH conditions. Preferably the active principlecombats free radicals, and/or UV radiation or the effects thereof,and/or pollution, and/or sunburn, and/or loss of firmness and/orelasticity.

[0024] Mention may be made, by way of example and without impliedlimitation, of: ascorbic acid and its derivatives, such as salts oresters thereof, particularly the 5,6-di-O-dimethylsilylascorbate (soldby Exsymol under the reference PRO-AA), the potassium salt ofdl-α-tocopheryl dl-ascorbyl phosphate (sold by Senju Pharmaceuticalunder the reference SEPIVITAL EPC), magnesium ascorbyl phosphate orsodium ascorbyl phosphate (sold by Roche under the reference Stay-C 50).Such principles may be present in any amount, preferably an amountsufficient to effect its purpose, such as for example 0.5, 1, 5, 25,etc. grams per 100 grams of composition.

[0025] In a particularly advantageous aspect, the oxidation-sensitivehydrophilic active principle is ascorbic acid.

[0026] According to the invention, the term “non-crosslinkedN-vinylimidazole polymer or copolymer” is understood to mean any polymercomprising N-vinylimidazole units and not comprising a crosslinkingagent. Copolymers suitable for the implementation of the invention arecopolymers combining N-vinylimidazole with N-vinylpyrrolidone and/orN-vinylcaprolactam subunits.

[0027] In an advantageous aspect of the invention, the copolymer has amolar fraction of N-vinylimidazole units of between 0.1 and 1, morepreferably between 0.4 and 0.9, inclusive.

[0028] According to an advantageous aspect of the invention, the molarratio of the N-vinylimidazole unit equivalent to the oxidation-sensitivehydrophilic active principle varies between 0.004 and 16 and preferablybetween 0.01 and 1, inclusive.

[0029] Use will preferably be made of anN-vinylimidazole/N-vinylpyrrolidone copolymer.

[0030] The weight-average molar mass of the N-vinylimidazole polymerswill advantageously be between 1 000 and 1×10⁷ and preferably between 5000 and 5×10⁶.

[0031] Use may be made, to this end, of thevinylpyrrolidone/vinylimidazole (50/50) copolymer having aweight-average molar mass of 1 200 000 sold under the reference LUVITECVPI 55K72W by BASF or the vinylpyrrolidone/vinylimidazole (50/50)copolymer having a weight-average molar mass of 10 000 sold under thereference LUVITEC VPI 55K18P by BASF.

[0032] The at least one polymer or copolymer is preferably present inthe composition according to the invention in an amount sufficient toproduce the desired effect, that is to say in an amount sufficient tostabilize the oxidation-sensitive hydrophilic active principle.Preferably, the copolymer is present at a concentration of between 0.1and 5% by weight with respect to the total weight of the aqueous phaseand more particularly at a concentration of between 0.1 and 2% by weightwith respect to the total weight of the aqueous phase, inclusive. Apreferred amount is a stabilizing amount, that is, an amount that slowsor prevents the oxidation of the active principle, for example at 45° C.for two months.

[0033] The compositions used according to the invention are intended inone embodiment for topical application to the skin and/or itssuperficial body growths and therefore preferably comprise aphysiologically acceptable medium, that is to say a medium compatiblewith cutaneous tissues, such as the skin, scalp, eyelashes, eyebrows,hair, nails and mucous membranes. This physiologically acceptable mediumcomprises an aqueous phase and optionally a physiologically acceptableorganic solvent chosen, for example, from lower alcohols comprising from1 to 8 carbon atoms and in particular from 1 to 6 carbon atoms, such asethanol, isopropanol, propanol or butanol; polyethylene glycols havingfrom 6 to 80 ethylene oxide units; or polyols, such as propylene glycol,isoprene glycol, butylene glycol, glycerol or sorbitol.

[0034] When the physiologically acceptable medium is an aqueous medium,it may have a pH which is compatible with the skin, preferably rangingfrom 3 to 9 and better still from 3.5 to 7.5.

[0035] The compositions according to the invention can be provided inany form, including any pharmaceutical dosage form used conventionallyfor topical application and in particular in the form of aqueous oraqueous/alcoholic solutions, of oil-in-water (O/W) or water-in-oil (W/O)or multiple (triple: W/O/W or O/W/O) emulsions, of aqueous gels or ofdispersions of a fatty phase in an aqueous phase using spherules, itbeing possible for these spherules to be polymeric nanoparticles, suchas nanospheres and nanocapsules, or lipid vesicles of ionic and/ornonionic type (liposomes, niosomes or oleosomes). These compositions areprepared according to the usual methods.

[0036] In addition, the compositions used according to the invention canbe more or less fluid and can have the appearance of a white or colouredcream, of an ointment, of a milk, of a lotion, of a serum, of a paste orof a foam. They can optionally be applied to the skin in the form of anaerosol. They can also be provided in a solid form, for example in theform of a stick.

[0037] When the compositions according to the invention comprise an oilyphase, the latter preferably comprises at least one oil. It canadditionally comprise other fatty substances.

[0038] Mention may be made, as oils which can be used in the compositionof the invention, of, for example:

[0039] hydrocarbonaceous oils of animal origin, such asperhydrosqualene;

[0040] hydrocarbonaceous oils of vegetable origin, such as liquidtriglycerides of fatty acids comprising from 4 to 10 carbon atoms, suchas triglycerides of heptanoic acid or octanoic acid, or alternatively,for example, sunflower, maize, soybean, gourd, grape seed, sesame,hazelnut, apricot, macadamia, arara, castor or avocado oils,triglycerides of caprylic/capric acids, such as those sold byStéarineries Dubois or those sold under the names Miglyol 810, 812 and818 by Dynamit Nobel, jojoba oil, or karite butter oil;

[0041] synthetic esters and ethers, in particular of fatty acids, suchas the oils of formulae R¹COOR² and R¹OR² in which R¹ represents theresidue of a fatty acid comprising from 8 to 29 carbon atoms and R²represents a branched or unbranched hydrocarbonaceous chain comprisingfrom 3 to 30 carbon atoms, such as, for example, purcellin oil, isononylisononanoate, isopropyl myristate, 2-ethylhexyl palmitate,2-octyldodecyl stearate, 2-octyldodecyl erucate or isostearylisostearate; hydroxylated esters, such as isostearyl lactate, octylhydroxystearate, octyldodecyl hydroxystearate, diisostearyl malate,triisocetyl citrate or heptanoates, octanoates or decanoates of fattyalcohols; polyol esters, such as propylene glycol dioctanoate, neopentylglycol diheptanoate and diethylene glycol diisononanoate; andpentaerythritol esters, such as pentaerythrityl tetraisostearate;

[0042] linear or branched hydrocarbons of mineral or synthetic origin,such as volatile or nonvolatile liquid paraffins and their derivatives,liquid petrolatum, polydecenes or hydrogenated polyisobutene, such asparleam oil;

[0043] fatty alcohols having from 8 to 26 carbon atoms, such as cetylalcohol, stearyl alcohol and their mixture (cetearyl alcohol),octyldodecanol, 2-butyloctanol, 2-hexyldecanol, 2-undecylpentadecanol,oleyl alcohol or linoleyl alcohol;

[0044] partially hydrocarbon-comprising and/or silicone-comprisingfluorinated oils, such as those disclosed in the document JP-A-2-295912;

[0045] silicone oils, such as volatile or nonvolatilepolymethylsiloxanes (PDMS) comprising a linear or cyclic silicone chainwhich are liquid or pasty at ambient temperature, in particularcyclopolydimethylsiloxanes (cyclomethicones), such as cyclohexasiloxane;polydimethylsiloxanes comprising pendent alkyl, alkoxy or phenyl groupsor alkyl, alkoxy or phenyl groups at the end of the silicone chain,which groups have from 2 to 24 carbon atoms; or phenylated silicones,such as phenyl trimethicones, phenyl dimethicones,phenyltrimethyl-siloxydiphenylsiloxanes, diphenyl dimethicones,diphenylmethyldiphenyltrisiloxanes,(2-phenylethyl)trimethylsiloxysilicates and polymethylphenylsiloxanes;

[0046] their mixtures.

[0047] The term “hydrocarbonaceous oil” is understood to mean, in thelist of the oils mentioned above, any oil predominantly comprisingcarbon and hydrogen atoms and optionally ester, ether, fluorinated,carboxylic acid and/or alcohol groups.

[0048] The other fatty substances which can be present in the oily phaseare, for example, fatty acids comprising from 8 to 30 carbon atoms, suchas stearic acid, lauric acid, palmitic acid and oleic acid; waxes, suchas lanolin, beeswax, carnauba or candelilla wax, paraffin or lignitewaxes or microcrystalline waxes, ceresin or ozokerite, or syntheticwaxes, such as polyethylene waxes or Fischer-Tropsch waxes; siliconeresins, such as trifluoromethyl C₁₋₄ alkyl dimethicone andtrifluoropropyl dimethicone; and silicone elastomers, such as theproducts sold under the names “KSG” by Shin-Etsu, under the names“Trefil”, “BY29” or “EPSX” by Dow Coming or under the names “Gransil” byGrant Industries.

[0049] These fatty substances can be chosen in a way varied by a personskilled in the art in order to prepare a composition having the desiredproperties, for example of consistency or of texture.

[0050] According to a specific embodiment of the invention, thecomposition according to the invention is a water-in-oil (W/O) oroil-in-water (O/W) emulsion. The proportion of the oily phase in theemulsion can range from 5 to 80% by weight and preferably from 5 to 50%by weight with respect to the total weight of the composition.

[0051] The emulsions generally comprise at least one emulsifier selectedfrom the group consisting of amphoteric, anionic, cationic or nonionicemulsifiers, used alone or as a mixture, and optionally a coemulsifier.The emulsifiers are appropriately chosen according to the emulsion to beobtained (W/O or O/W). The emulsifier and the coemulsifier are generallypresent in the composition in a proportion ranging from 0.3 to 30% byweight and preferably from 0.5 to 20% by weight with respect to thetotal weight of the composition.

[0052] Mention may be made, for the W/O emulsions, for example, asemulsifiers, of dimethicone copolyols, such as the mixture ofcyclomethicone and of dimethicone copolyol sold under the name “DC 5225C” by Dow Corning, and alkyl dimethicone copolyols, such as thelaurylmethicone copolyol sold under the name “Dow Corning 5200Formulation Aid” by Dow Corning and the cetyl dimethicone copolyol soldunder the name Abil EM 90^(R) by Goldschmidt. Use may also be made, assurfactant of W/O emulsions, of a crosslinked solid organopolysiloxaneelastomer comprising at least one oxyalkylenated group, such as thoseobtained according to the procedure of Examples 3, 4 and 8 of thedocument U.S. Pat. No. 5,412,004 and the examples of the document U.S.Pat. No. 5,811,487, in particular the product of Example 3 (syntheticexample) of U.S. Pat. No. 5,412,004, and such as that sold under thereference KSG 21 by Shin Etsu. Use may also be made, as emulsifier, of apolyolefin-derived oligomer or polymer comprising a succinic ending; thelatter is preferably a polyolefin comprising an esterified or amidatedsuccinic ending or a salt of such a polyolefin and in particularpolyisobutylene comprising an esterified or amidated succinic endingsuch as the products sold under the names L5603 and L2721 and OS131769by Lubrizol.

[0053] Mention may be made, for the O/W emulsions, for example, asemulsifiers, of nonionic emulsifiers, such as esters of fatty acids andof glycerol which are oxyalkylenated (more particularlypolyoxyethylenated); esters of fatty acids and of sorbitan which areoxyalkylenated; esters of fatty acids which are oxyalkylenated(oxyethylenated and/or oxypropylenated); ethers of fatty alcohols whichare oxyethylenated (oxyethylenated and/or oxypropylenated); sugaresters, such as sucrose stearate; and their mixtures, such as themixture of glyceryl stearate and of PEG-40 stearate.

[0054] The compositions of the invention can also comprise adjuvantsconventional in the cosmetics or dermatological field, such ashydrophilic or lipophilic gelling agents, preservatives, solvents,fragrances, fillers, UV screening agents, bactericides, odour absorbers,colouring materials, plant extracts or salts. The amounts of thesevarious adjuvants are those generally used in the field underconsideration, for example from 0.01 to 20% of the total weight of thecomposition. These adjuvants, depending on their nature, can beintroduced into the fatty phase, into the aqueous phase and/or into thelipid spherules.

[0055] Mention may be made, as fillers which can be used in thecomposition of the invention, for example, of pigments, silica powder;talc; particles of polyamide and in particular those sold under the nameOrgasol by Atochem; polyethylene powders; microspheres based on acryliccopolymers, such as those made of ethylene glycol dimethacrylate/laurylmethacrylate copolymer which are sold by Dow Coming under the namePolytrap; expanded powders, such as hollow microspheres and inparticular the microspheres sold under the name Expancel by KemanordPlast or under the name Micropearl F 80 ED by Matsumoto; silicone resinmicrobeads, such as those sold under the name Tospearl by ToshibaSilicone; and their mixtures. These fillers can be present in amountsranging from 0 to 20% by weight and preferably from 1 to 10% by weightwith respect to the total weight of the composition.

[0056] According to a preferred embodiment, the compositions inaccordance with the invention can additionally comprise at least oneorganic photoprotective agent and/or at least one inorganicphotoprotective agent distinct from the above active principle which isactive in the UV-A and/or UV-B regions (absorbers), and which aresoluble in water or in fats or else are insoluble in the cosmeticsolvents commonly used.

[0057] The organic photoprotective agents are not limited and may bechosen in particular from anthranilates; cinnamic derivatives;dibenzoylmethane derivatives; salicylic derivatives; camphorderivatives; triazine derivatives, such as those disclosed in PatentApplications U.S. Pat. No. 4,367,390, EP 863 145, EP 517 104, EP 570838, EP 796 851, EP 775 698, EP 878 469, EP 933 376, EP 507 691, EP 507692, EP 790 243 and EP 944 624; benzophenone derivatives;-diphenylacrylate derivatives; benzotriazole derivatives; benzalmalonatederivatives; benzimidazole derivatives; imidazolines; bisbenzoazolylderivatives as disclosed in Patents EP 669 323 and U.S. Pat. No.2,463,264; p-aminobenzoic acid (PABA) derivatives;methylenebis(hydroxyphenylbenzotriazole) derivatives as disclosed inApplications U.S. Pat. No. 5,237,071, U.S. Pat. No. 5,166,355, GB 2 303549, DE 197 26 184 and EP 893 119; screening polymers and screeningsilicones, such as those disclosed in particular in Application WO93/04665; dimers derived from -alkylstyrene, such as those disclosed inPatent Application DE 198 55 649; 4,4-diarylbutadienes as disclosed inApplications EP 0 967 200, DE 197 46 654, DE 197 55 649, EP-A-1 008 586,EP 1 133 980 and EP 133 981; and their mixtures.

[0058] By way of illustration, mention may be made, as photoprotectiveagents which are active in the UV-A and/or UV-B regions, denoted belowunder their INCI names, of:

[0059] p-aminobenzoic acid (PABA) derivatives, in particular PABA, ethylPABA, ethyl dihydroxypropyl PABA, ethylhexyl dimethyl PABA (sold inparticular under the name “Escalol 507” by ISP), glyceryl PABA or PEG-25PABA (sold under the name “Uvinul P25” by BASF),

[0060] salicylic derivatives, in particular homosalate (sold under thename “Eusolex HMS” by Rona/EM Industries), ethylhexyl salicylate (soldunder the name “Neo Heliopan OS” by Haarmann and Reimeri), dipropyleneglycol salicylate (sold under the name “Dipsal” by Scher), or TEAsalicylate (sold under the name “Neo Heliopan TS” by Haarmann andReimer),

[0061] dibenzoylmethane derivatives, in particular butylmethoxydibenzoylmethane (sold in particular under the trade name “Parsol1789” by Hoffmann-LaRoche), or isopropyl dibenzoylmethane,

[0062] cinnamic derivatives, in particular ethylhexyl methoxycinnamate(sold in particular under the trade name “Parsol MCX” byHoffmann-LaRoche), isopropyl methoxycinnamate, isoamyl methoxycinnamate(sold under the trade name “Neo Heliopan E 1000” by Haarmann andReimer), cinoxate, DEA methoxycinnamate, diisopropyl methyl cinnamate,or glyceryl ethylhexanoate dimethoxycinnamate,

[0063] , -diphenylacrylate derivatives, in particular octocrylene (soldin particular under the trade name “Uvinul N539” by BASF) or etocrylene(sold in particular under the trade name “Uvinul N35” by BASF),

[0064] benzophenone, in particular benzophenone-1 (sold under the tradename “Uvinul 400” by BASF), benzophenone-2 (sold under the trade name“Uvinul D50” by BASF), benzophenone-3 or oxybenzone (sold under thetrade name “Uvinul M40” by BASF), benzophenone-4 (sold under the tradename “Uvinul MS40” by BASF), benzophenone-5, benzophenone-6 (sold underthe trade name “Helisorb 11” by Norquay), benzophenone-8 (sold under thetrade name “Spectra-Sorb UV-24” by American Cyanamid), benzophenone-9(sold under the trade name “Uvinul DS-49” by BASF), benzophenone-12, orn-hexyl 2-(4-diethylamino-2-hydroxybenzoyl)benzoate,

[0065] benzylidene camphor derivatives, in particular 3-benzylidenecamphor (manufactured under the name “Mexoryl SD” by Chimex),4-methylbenzylidene camphor (sold under the name “Eusolex 6300” byMerck), benzylidene camphor sulphonic acid (manufactured under the name“Mexoryl SL” by Chimex), camphor benzalkonium methosulphate(manufactured under the name “Mexoryl SO” by Chimex), terephthalylidenedicamphor sulphonic acid (manufactured under the name “Mexoryl SX” byChimex), or polyacrylamidomethyl benzylidene camphor (manufactured underthe name “Mesoryl SW” by Chimex),

[0066] benzimidazole derivatives, in particular phenylbenzimidazolesulphonic acid (sold in particular under the trade name “Eusolex 232” byMerck), or disodium phenyl dibenzimidazole tetrasulphonate (sold underthe trade name “Neo Heliopan AP” by Haarmann and Reimer),

[0067] triazine derivatives, in particular anisotriazine (sold under thetrade name “Tinosorb S” by Ciba Specialty Chemicals), ethylhexyltriazone (sold in particular under the trade name “Uvinul T150” byBASF), diethylhexyl butamido triazone (sold under the trade name“Uvasorb HEB” by Sigma 3V) or 2,4,6-tris(diisobutyl4′-amino-benzalmalonate)-s-triazine,

[0068] benzotriazole derivatives, in particular drometrizole trisiloxane(sold under the name “Silatrizole” by Rhodia Chimie) or methylenebisbenzotriazolyl tetramethylbutylphenol (sold in the solid form underthe trade name “Mixxim BB/100” by Fairmount Chemical or in themicronized form in aqueous dispersion under the trade name “Tinosorb M”by Ciba Specialty Chemicals),

[0069] anthranilic derivatives, in particular menthyl anthranilate (soldunder the trade name “Neo Heliopan MA” by Haarmann and Reimer),

[0070] imidazoline derivatives, in particular ethylhexyldimethoxybenzylidene dioxoimidazoline propionate,

[0071] benzalmalonate derivatives, in particular polyorganosiloxanecomprising benzalmalonate functional groups (sold under the trade name“Parsol SLX” by Hoffmann-LaRoche),

[0072] 4,4-diarylbutadiene derivatives, in particular 1,1′-dicarboxy(2,2′-dimethylpropyl)-4,4-diphenylbutadiene,

[0073] and their mixtures.

[0074] The organic photoprotective agents which are more particularlypreferred are selected from the group consisting of ethylhexylsalicylate, ethylhexyl methoxycinnamate, octocrylene,phenylbenzimidazole sulphonic acid, benzophenone-3, benzophenone-4,benzophenone-5, 4-methylbenzylidene camphor, terephthalylidene dicamphorsulphonic acid, disodium phenyl dibenzimidazole tetrasulphonate,2,4,6-tris(diisobutyl 4′-aminobenzalmalonate)-s-triazine, anisotriazine,ethylhexyl triazone, diethylhexyl butamido triazone, methylenebisbenzotriazolyl tetramethylbutylphenol, drometrizole trisiloxane,1,1′-dicarboxy (2,2′-dimethylpropyl)-4,4-diphenylbutadiene, and theirmixtures.

[0075] The inorganic photoprotective agents may be selected from thegroup consisting of pigments or alternatively nanopigments (mean size ofthe primary particles: generally between 5 nm and 100 nm, preferablybetween 10 nm and 50 nm) formed from coated or uncoated metal oxides,such as, for example, titanium oxide (amorphous or crystalline in therutile and/or anatase form), iron oxide, zinc oxide, zirconium oxide orcerium oxide nanopigments, which are all UV photoprotective agents wellknown per se. Conventional coating agents are, furthermore, aluminaand/or aluminium stearate. Such nanopigments formed from coated oruncoated metal oxides are disclosed in particular in Patent ApplicationsEP 518 772 and EP 518 773.

[0076] The photoprotective agents may generally be present in thecompositions according to the invention in proportions ranging from 0.1to 20% by weight with respect to the total weight of the composition andpreferably ranging from 0.2 to 15% by weight with respect to the totalweight of the composition.

[0077] In another advantageous aspect of the invention, the compositioncan additionally comprise at least one other agent selected from thegroup consisting of scavengers for ozone, scavengers for heavy metalsand agents for combatting free radicals.

[0078] Mention may in particular be made, as scavengers for ozone whichcan be used in the composition according to the invention, of phenolsand polyphenols, in particular tannins, ellagic acid and tannic acid;epigallocatechin and the natural extracts comprising it; olive tree leafextracts; tea extracts, in particular green tea extracts; anthocyanins;rosemary extracts; phenolic acids, in particular chorogenic acid;stilbenes, in particular resveratrol; sulphur-comprising amino acidderivatives, in particular S-carboxymethylcysteine; ergothioneine;N-acetylcysteine; chelating agents, such asN,N′-bis(3,4,5-trimethoxybenzyl)ethylenediamine or one of its salts,metal complexes or esters; carotenoids, such as crocetin; and variousstarting materials, such as the mixture of arginine, histidineribonucleate, mannitol, adenosine triphosphate, pyridoxine,phenylalanine, tyrosine and hydrolysed RNA sold by LaboratoiresSérobiologiques under the trade name CPP LS 2633-12F®, the water-solublemaize fraction sold by Solabia under the trade name Phytovityl®, themixture of fumitory extracts and of lemon extracts sold under the nameUnicotrozon C-49® by Induchem and the mixture of extracts of ginseng, ofapple, of peach, of wheat and of barley sold by Provital under the tradename Pronalen Bioprotect®.

[0079] Finally, mention may in particular be made, as scavengers forheavy metals which can be used in the composition according to theinvention, of chelating agents, such as EDTA, the pentasodium salt ofethylenediaminetetramethylenephosphonic acid, andN,N′-bis(3,4,5-trimethoxybenzyl)ethylenediamine or one of its salts,metal complexes or esters; phytic acid; chitosan derivatives; teaextracts, in particular green tea extracts, tannins, such as ellagicacid; sulphur-comprising amino acids, such as cysteine; water hyacinth(Eichomia crassipes) extracts; and the water-soluble maize fraction soldby Solabia under the trade name Phytovityl®.

[0080] The agents for combatting free radicals which can be used in thecomposition according to the invention comprise, in addition to certainagents for combatting pollution mentioned above, vitamin E and itsderivatives, such as tocopheryl acetate; bioflavonoids; coenzyme Q10 orubiquinone; certain enzymes, such as catalase, superoxide dismutase,lactoperoxidase, glutathione peroxidase and quinone reductases;glutathione; benzylidene camphor; benzylcyclanones; substitutednaphthalenones; pidolates; phytantriol; γ-oryzanol; lignans; andmelatonin.

[0081] The composition according to the invention can be applied forexample to the skin or lips. It can thus be used in a cosmetic treatmentprocess for the purpose of preventing or combatting the harmful effectsof UV radiation and/or of pollution on the skin or mucous membranes,comprising the application of the composition according to the inventionto the skin or mucous membranes.

[0082] The invention also relates to a cosmetic treatment process forthe purpose of preventing or combatting loss of firmness and/or ofelasticity of the skin or mucous membranes, comprising the applicationof the composition according to the invention to the skin or mucousmembranes.

[0083] The composition according to the invention can also be used forthe manufacture of a dermatological preparation comprising an aqueousphase which is intended to prevent or combat harmful effects of UVradiation and/or of pollution on the skin.

[0084] In another embodiment, the composition according to the inventioncan be used for the manufacture of a dermatological preparationcomprising an aqueous phase which is intended to prevent or combat lossof firmness and/or elasticity of the skin.

[0085] The examples which follow serve to illustrate the inventionwithout, however, exhibiting a limiting nature. The compounds are,depending on the situation, cited according to chemical names oraccording to CTFA (International Cosmetic Ingredient Dictionary andHandbook) names.

EXAMPLES Example 1 Accelerated Storage Test

[0086] The aim of this test is to study the decomposition of anoxidation-sensitive hydrophilic active principle after storing for twomonths at 45° C. Various solutions were prepared and their compositionsare collated in the following table: TABLE I Compositions (in Solution Awater) (Control) Solution B Solution C Solution D Ascorbic acid 15% 15%15% 15% Polymer 1 —  1% — — Polymer 2 — —  1% — Polymer 3 — — —  1%

[0087] All the solutions are brought to pH 6 with 8.9 mol/l KOH.

[0088] The percentages of the polymers are given as active material.

[0089] Polymer 1: Vinylpyrrolidone/vinylimidazole (50/50) copolymer soldunder the reference Luvitec VPI 55K72W of BASF (Weight-average molecularmass 1.2×10⁶).

[0090] Polymer 2: Vinylpyrrolidone/vinylimidazole (50/50) copolymer soldunder the reference Luvitec VPI 55K18P of BASF (Weight-average molecularmass 10 000).

[0091] Polymer 3: Polyvinylpyrrolidone sold under the reference Kollidon12PF of BASF (Weight-average molecular mass 3 000).

[0092] The degree of decomposition measured is given by the ratio:

(C₀-C₂ months)/CO

[0093] with C₀ concentration of ascorbic acid at t=0 and C_(2 months)the concentration of ascorbic acid at t=2 months, under the conditionsindicated in the above table.

[0094] The concentration of ascorbic acid is determined by the HPLCtechnique (LaChrom Merck system). The analytical conditions are asfollows:

[0095] Column: Lichrosphere100 RP18 (250 mm)

[0096] Eluent: 0.1M phosphate buffer, pH 2.1

[0097] Flow rate: 1 ml/min

[0098] Detection at 257 nm

[0099] Dilution of the sample such that the concentration of ascorbicacid is between 0.05 and 1 mg/ml.

[0100] The results obtained are collated in the following Table II:TABLE II Degree of decomposition after 2 months at 45° C. (in %) underair, amber glass bottle under nitrogen, aluminium flask Solution A 4319.4 Solution B 10.8 1 Solution C 23.4 4.5 Solution D 35.8 15.7

[0101] It is found, from Table II, that the stability of ascorbic acidis improved in the presence of Polymer 1 and Polymer 2 of the invention,even in the presence of atmospheric oxygen, in comparison with thecontrol. It is also found that the N-vinylpyrrolidone homopolymer aloneis not sufficient to effectively stabilize the ascorbic acid solution.

[0102] As the polymers mentioned are hydrophilic, it would be sufficientto add them to an aqueous ascorbic acid solution to stabilize theascorbic acid.

Example 2 Demonstration of the Activity in Combatting Free Radicals

[0103] I. Principle

[0104] This test makes it possible to evaluate the effect of a moleculein combatting OH^(o).

[0105] It is based on the measurement by gas chromatography of theethylene formed from the oxidation of methionine by the hydroxylradical. The latter is generated by a ferro-catalysed Fenton reactionmaintained by the continuous generation of superoxide anions. The anionsO2^(o)—are produced by photochemical reduction at 365 nm of riboflavin(RBF) by a hydrogen donor, according to the following scheme:

RBFH₂+O₂→RBF+2 O₂ ^(o−)+2H⁺

2 O₂ ^(o−)+2H⁺→H₂O₂+O₂

O₂ ^(o−)+L—Fe³⁺→O₂+L—Fe²⁺

H₂O₂+L—Fe²⁺→L—Fe³⁺+OH⁻+OH^(o)

CH₃—S—CH₂—CH(COOH)—NH₂+OH^(o)→CH₂=CH₂+products

[0106] The neutralization of the OH^(o) radicals is reflected byinhibition of the production of ethylene.

[0107] II. Procedure

[0108] Irradiation equipment: 3 low-pressure mercury vapour tubes.

[0109] The tested products are dissolved in a phosphate buffer. They aretested at final concentrations in the reaction mixture generally rangingfrom 0.1 to 3%, according to their solubility. The final volume is 2 ml.

[0110] The separation distance for exposure under the UV bank isadjusted in order to have an exposure time of approximately 8 minutesfor a UV-A dose of 1 joule/cm² and in order not to adjust this settingthroughout the duration of the test.

[0111] The following are introduced in this order into a head spaceflask:

[0112] 1.4 ml of phosphate buffer

[0113] 100 μl of 200 mM methionine solution

[0114] 100 μl of 4 mM ferric chloride solution

[0115] 100 μl of phosphate buffer, pH 7.4, (control) or of solutioncomprising the active principle to be tested

[0116] 100 μl of 4 mM EDTA solution

[0117] 100 μl of 400 mM NADH solution

[0118] The samples and the blanks are all prepared in succession and arekept sheltered from the light.

[0119] The UV-A bank is switched on, displaying a number of joules atleast equal to the number of samples. The samples are irradiated one byone at intervals of 0.5 joules.

[0120] Every 0.5 joules:

[0121] 100 μl of riboflavin are added

[0122] mixing is carried out

[0123] the sample is irradiated with 1 joule

[0124] the reaction is halted with 0.5 ml of IN NaOH

[0125] the sample is sheltered from the light

[0126] The flasks are inserted into the sample changer of thechromatograph. The ethylene peak exits at a retention time ofapproximately 2.00 minutes. A minimum of 3 measurements are carried outper sample.

[0127] III. Results:

[0128] The results are expressed as percentage of inhibition ofproduction of ethylene with respect to the control solution.

[0129] It is apparent that, for the tested samples comprising theascorbic acid and N-vinylimidazole/N-vinylpyrrolidone copolymercombination, inhibition of the production of ethylene is increased withrespect to the control, thus demonstrating the activity in combattingfree radicals of this combination.

Example 3 O/W cream

[0130] The following composition is prepared in a way conventional to aperson skilled in the art. Glyceryl stearate and PEG-100 stearate 2.5 gPEG-50 stearate 2.5 g Cetyl alcohol 1 g Stearyl alcohol 1 g Hydrogenatedpolyisobutene 5 g Water 12.23 g Glycerol 5 g Cyclopentasiloxane 15 gCarbomer 0.6 g Phenoxyethanol 1 g Water 45.17 g Ascorbic acid 5 gPotassium hydroxide (50% solution) 3 g Vinylpyrrolidone/vinylimidazolecopolymer 1 g

[0131] This soft cream, on application, makes it possible to smooth outthe lines of the face and exhibits good stability for ascorbic acid.

Example 4 W/O emulsion

[0132] The following composition is prepared in a way conventional to aperson skilled in the art. Water 45.17 g Ascorbic acid 5 g Potassiumhydroxide (50% solution) 3 g Vinylpyrrolidone/vinylimidazole copolymer 1g Glycerol 5 g Phenoxyethanol 1 g Cyclopentasiloxane and dimethiconecopolyol 20 g Phenyl trimethicone 4 g Prunus armeniaca (apricot) kerneloil 3.5 g Dimethicone and 5 g Dimethicone/vinyl dimethicone crosspolymerNylon-12 5 g

[0133] A white water-in-oil emulsion is obtained, which emulsion iscapable of smoothing out the lines of the face and in which emulsionascorbic acid has good stability.

[0134] The above description, as illustrated by non-limiting examples,allows one of ordinary skill in the art to make and use a compositionfor preventing or combatting the harmful effects of UV radiation and/orof pollution on the skin comprising, preferably in a physiologicallyacceptable medium comprising an aqueous phase, at least oneoxidation-sensitive hydrophilic active principle selected from the groupconsisting of ascorbic acid and its derivatives and at least onenon-crosslinked N-vinylimidazole polymer or copolymer, the activeprinciple and the polymer or copolymer both being present in the aqueousphase. Also provided is a method for preventing or combatting loss offirmness and/or of elasticity of the skin, for soothing sunburn, and toprevent or combat the harmful effects of UV radiation and/or ofpollution on the skin using this composition, and the use of acombination composed of at least one oxidation-sensitive hydrophilicactive principle selected from the group consisting of ascorbic acid andits derivatives and of at least one non-crosslinked N-vinylimidazolepolymer or copolymer in the aqueous phase of a cosmetic composition asagent for combatting free radicals. Further provided is a cosmetictreatment process to prevent or combat the harmful effects of UVradiation and/or of pollution on the skin or mucous membranes,comprising the application, to the skin or mucous membranes, of acomposition comprising, preferably in a physiologically acceptablemedium comprising an aqueous phase, at least one oxidation-sensitivehydrophilic active principle selected from the group consisting ofascorbic acid and its derivatives and at least one non-crosslinkedN-vinylimidazole polymer or copolymer, the active principle and saidpolymer or copolymer both being present in the aqueous phase, and acosmetic process to combat loss of firmness and/or of elasticity of theskin or mucous membranes, comprising the application, to the skin ormucous membranes, of a composition comprising, preferably in aphysiologically acceptable medium comprising an aqueous phase, at leastone oxidation-sensitive hydrophilic active principle selected from thegroup consisting of ascorbic acid and its derivatives and at least onenon-crosslinked N-vinylimidazole polymer or copolymer, the activeprinciple and the polymer or copolymer both being present in the aqueousphase.

[0135] French patent application 0115375 is incorporated herein byreference, as are all references, texts, documents, articles, standards,patents, applications, etc., mentioned above. All numerical rangesinclude all values therebetween as if specifically written out.

[0136] Also incorporated herein by reference are the following U.S.applications, all filed Nov. 27, 2002, where the present application islisted for information only: U.S. Ser. No. . . . (Atty. Docket230634US0) U.S. Ser. No. . . . (Atty. Docket 230608US0) U.S. Ser. No. .. . (Atty. Docket 230616US0) U.S. Ser. No. . . . (Atty. Docket230614US0) U.S. Ser. No. . . . (Atty. Docket 230615US0)

1. A method for treating skin and/or mucous membrane, comprisingapplying to skin or mucous membrane a composition comprising, in aphysiologically acceptable medium comprising an aqueous phase, at leastone oxidation-sensitive hydrophilic active principle selected from thegroup consisting of ascorbic acid and its derivatives and at least onenon-crosslinked N-vinylimidazole polymer or copolymer, the at least oneactive principle and the at least one polymer or copolymer both beingpresent in the aqueous phase.
 2. The method of claim 1, wherein saidtreating is selected from the group consisting of preventing orcombatting harmful effects of UV radiation and/or of pollution,preventing or combatting loss of firmness and/or of elasticity,combatting free radicals, and soothing sunburn, said method comprisingapplying an amount of said composition to skin and/or mucous membrane toso treat.
 3. The method of claim 2, wherein said treating is preventingor combatting harmful effects of UV radiation and/or of pollution. 4.The method of claim 2, wherein said treating is preventing or combattingloss of firmness and/or of elasticity.
 5. The method of claim 2, whereinsaid treating is combatting free radicals.
 6. The method of claim 2,wherein said treating is soothing sunburn.
 7. The method according toclaim 1, wherein the ascorbic acid derivatives are selected from thegroup consisting of ascorbic acid esters and ascorbic acid salts.
 8. Themethod according to claim 1, wherein the hydrophilic active principle isselected from the group consisting of 5,6-di-O-dimethylsilylascorbate,dl-α-tocopheryl dl-ascorbyl phosphate potassium salt, magnesium ascorbylphosphate and sodium ascorbyl phosphate.
 9. The method according toclaim 1, wherein the oxidation-sensitive hydrophilic active principle isascorbic acid.
 10. The method according to claim 1, wherein thecomposition comprises a non-crosslinked copolymer that is a combinationof the N-vinylimidazole with N-vinylpyrrolidone and/orN-vinylcaprolactam subunits.
 11. The method according to claim 1,wherein the composition comprises a non-crosslinked copolymer that is anN-vinylimidazole/N-vinylpyrrolidone copolymer.
 12. The method accordingto claim 1, wherein the composition comprises a non-crosslinkedcopolymer that is selected from the group consisting of avinylpyrrolidone/vinylimidazole (50/50) copolymer having aweight-average molar mass of 1 200 000 and avinylpyrrolidone/vinylimidazole (50/50) copolymer having aweight-average molar mass of 10
 000. 13. The method according to claim1, wherein a molar ratio of N-vinylimidazole unit equivalent to theoxidation-sensitive hydrophilic active principle is from 0.004 to 16.14. The method according to claim 13, wherein the molar ratio of theN-vinylimidazole unit equivalent to the oxidation-sensitive hydrophilicactive principle varies between 0.01 and
 1. 15. The method according toclaim 1, wherein the polymer or copolymer is present at a concentrationof 0.1 to 5% by weight of the aqueous phase.
 16. The method according toclaim 13, wherein the polymer or copolymer is present at a concentrationof 0.1 to 2% by weight of the aqueous phase.
 17. The method according toclaim 1, wherein the polymer or copolymer has a molar fraction ofN-vinylimidazole units of 0.1 to
 1. 18. The method according to claim15, wherein the polymer or copolymer has a molar fraction ofN-vinylimidazole units of 0.4 to 0.9.
 19. The method according to claim1, wherein the composition further comprises an agent in addition to thehydrophilic active principle selected from the group consisting ofscavengers for ozone, scavengers for heavy metals and agents forcombatting free radicals.